A Modulation Format Identification Method Based on Amplitude Deviation Analysis of Received Optical Communication Signal

Modulation format identification (MFI) is necessary for future elastic optical networks. We propose an MFI scheme based on the amplitude deviation analysis of the received optical communication signal. In our method, for a received optical signal, two values of normalized average amplitude deviation with reference to amplitude of ideal polarization-division multiplexing (PDM) QPSK and 16 quadratic-amplitude modulation (QAM) are computed, respectively, and the ratio of the two values is used to identify the commonly used formats like PDM-QPSK, PDM-8 QAM, PDM-16 QAM, PDM-32 QAM, and PDM-64 QAM. The results demonstrate that the modulation format can be identified with the required optical signal-to-noise ratio not higher than the forward error correction (FEC) threshold. The advantage of our method is that it is not sensitive to phase noise, frequency offset, and nonlinearity in optical fiber communication systems. The proposed method needs no training samples or additional hardware, so it is simple and cost-effective. Meanwhile, we also discuss the influence of the residual chromatic dispersion on our proposed scheme.